lkdtm: remove duplicated include of init.h

Fix following checkincludes.pl warning:
./drivers/misc/lkdtm/core.c
26	#include <linux/init.h>
    29	#include <linux/init.h>

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Link: https://lore.kernel.org/r/20210628123512.38090-1-wanjiabing@vivo.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/lkdtm/core.c

@@ -26,7 +26,6 @@
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/debugfs.h>
-#include <linux/init.h>
 
 #define DEFAULT_COUNT 10